1. Field of the Invention
The present invention relates to a laser oscillator comprising a heat exchanger which cools a gas medium.
2. Description of the Related Art
In a gas laser oscillator using a gas medium, such as a carbon dioxide gas laser oscillator, the gas medium circulates at a high speed. In the gas laser oscillator, foreign matters may be mixed in the gas medium. The foreign matters include fine dust, dirt, or a particle which is mixed in during assembly, a quartz powder produced due to an excitation electric discharge in an electric discharge tube, an abrasion powder of a wall surface of a gas flow channel which is produced due to the gas medium circulating at a high speed, and the like.
A surface of a partial reflection mirror and a total reflection mirror which constitute the oscillator is subjected to coating which contributes to oscillation of laser light. When the foreign matters adhere to a surface of an optical component, such as the partial reflection mirror and the total reflection mirror, the laser light is absorbed and heat is generated. Further, it is liable to cause reduction of a laser output, deterioration of the optical components due to burning of the foreign matters, and the like. Accordingly, a dust collector which separates and collects a particulate material from the gas medium is attached to the gas laser oscillator. For the dust collector, a type such as a cyclone type is adopted. In a cyclone type dust collector, dust and dirt contained in the gas medium can be centrifugally separated by swirling a gas.
Japanese Laid-open Patent Publication No. 2003-283008 discloses a laser oscillator comprising a dust collection mechanism which collects particulate foreign matters in a gas medium. In the dust collection mechanism, a gas medium containing the particulate foreign matters moves in the interior of a tube of a swirl part from top to bottom while swirling. In the meantime, the foreign matters having a greater specific gravity in comparison with the gas medium are centrifugally separated and fall down to a dust collection part to be heaped up.
In the laser oscillator in which the gas medium circulates, a remaining energy which has not been converted into laser light out of an energy which has excited the gas medium by an electric discharge and the like turns into heat of the gas medium. Further, when the gas medium is compressed by a blower, a temperature increases. To the laser oscillator, a heat exchanger is attached to cool the gas medium having the temperature increased due to an electric discharge and a drive of the blower.
Japanese Laid-open Patent Publication No. 2006-116472 discloses a cyclone comprising a heat exchanger. This publication discloses disposing a jacket which makes the gas to flow around an outer periphery of a tubular casing and performing heat exchange between the gas introduced into the jacket and an exhaust gas having a high temperature.
When the foreign matters adhere to the surface of the optical component and the laser output decreases, the optical component is detached and cleaning is performed. Alternatively, the optical component needs to be replaced. When the optical component is attached again, a skilled technique and a large amount of time are needed for light axis adjustment and the like. In addition, in a laser having a large output, when the laser light is radiated over the optical component to which the foreign matters adhere, the foreign matters are burned. Further, the foreign matters absorb the laser light and a temperature locally increases so that a coating of the optical component may be damaged. Also in this case, replacing the optical component is needed, and a skilled technique and a large amount of time are needed. Thus, the foreign matters are preferably removed as much as possible from the gas medium.
Further, a dust collection unit and a heat exchanger which are provided to the laser oscillator in which the gas medium circulates at a high speed are large and expensive. In the laser oscillator disclosed in Japanese Laid-open Patent Publication No. 2003-283008, a heat exchanger and a dust collector are separately disposed. Accordingly, a large space in which the heat exchanger and the dust collector are disposed is needed. Further, a tube for connection of the heat exchanger and the dust collector is needed so that a space in which the tube is disposed is needed. In addition, an operation for connection of the heat exchanger and the dust collector is needed. The cyclone disclosed in Japanese Laid-open Patent Publication No. 2006-116472 has a function of cooling a gas. However, in a structure in which the jacket which makes the gas to flow around the outer periphery of the tubular casing is disposed, a gas cooling ability is low.